This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-197105, filed Jun. 29, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a print board having a signal layer serving as a transmission line for high-speed signals, and an electronic device such as a portable computer equipped with the print board.
2. Description of the Related Art
A multi-layer print board to cope with increases in the speed of signal transmission is widely used in a circuit system, such as a Rambus memory, for processing high-speed signals in the 1 GHz band.
A print board, in which a signal layer and a ground layer both as a surface layer are layered with an insulation layer interposed therebetween, is known as that of the above-mentioned type. This signal layer is formed in a predetermined line pattern and functions as a transmission line for transmitting high-speed signals. In such conventional print boards, the thickness of the insulation layer isolating the signal layer from the ground layer, and the line width of the signal layer are set so as to keep the characteristic impedance of the signal layer (transmission line) on the ground layer at a desired value.
The signal layer of the print board has pads provided on terminal points and/or middle portions of the transmission line for soldering thereto various types of circuit components such as a semiconductor package or a connector. The size of the pads on the transmission line is determined in light of the conditions for soldering such a circuit component or manufacturing the pads. Accordingly, there may be a difference between the width of the pads and the line width of the signal layer.
If, in particular, the pads are wider than the line width of the transmission line, the continuity of the impedance of the signal layer is interrupted at the boundary of the transmission line and each pad, with the result that variations in the impedance become conspicuous when a high-speed signal passes through the boundary. These impedance variations adversely affect signal transmission on the transmission line, thereby degrading the transmission quality.
Accordingly, the present invention is directed to method and apparatus that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
In accordance with the purpose of the invention, as embodied and broadly described, the invention is directed to a print board comprising a signal layer formed in a predetermined line pattern to serve as a transmission line for transmitting high-speed signals; and an electrical connector formed on the signal layer, connected to the transmission line, and having a width which is substantially equal to a width of the transmission line.
According to the present invention, it is possible to prevent variations in the impedance of the transmission line to thereby improve the quality of transmission.
Additional objects and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention.
The objects and advantages of the present invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.